Copyright Goodheart-Willcox Co., Inc. 51 Chapter 2 Network Media—Copper-Core Cable Electronic terminology often requires an extensive background in electronics theory to fully grasp the concept being introduced. As networking has evolved over time, network technicians have coined their own terminology and have used electronics terms in some contexts that have slightly changed the original meaning of the term. Several of these terms and their infl uence on the data rate of data transmission are introduced in this section. Bandwidth Bandwidth is a measurement of the network media’s ability to carry data. Th e defi ni- tion of bandwidth varies according to the context to which it is applied. For example, when referring to a network cable, bandwidth refers to the amount of digital signal the cable can carry based on a given time. Network cable bandwidth is measured in bits per second (bps). Th e term bandwidth, when applied to network cabling, can be confused with the term frequency. Technically speaking, frequency is a measurement of the net- work media’s ability to carry an electronic signal. For example, a network cable can have a frequency rating of 250 MHz but a permissible bandwidth of 1000 MHz. Th e frequency rating is the rating of the individual wires inside the cable assembly the bandwidth is the ability of the entire cable assembly (four pairs of conductors) to carry digital signals. In general, the higher the bandwidth, the more data that can be carried. Please take note of the fact that bandwidth does not always match data rates because data rates can be infl uenced by data compression techniques. When referring to an analog signal, the term bandwidth means a measure- ment of the maximum frequency of a device or the total range of analog frequencies. Bandwidth in analog transmissions is measured in hertz (Hz). A range of frequencies would be all analog signal frequencies between two specifi c frequencies. An example would be television or radio analog signals transmitted and identifi ed as channels. A typical television channel is assigned a 6-MHz bandwidth. Th e bandwidth of analog transmission can support several diff erent frequen- cies at once, whereas, the bandwidth of digital transmission usually supports only one frequency. In other words, when data is transmitted over a cable using a digital signal, the digital signal uses the entire bandwidth. When data is transmitted over a cable using analog signals, many diff erent analog signals, or frequencies, represent- ing data can be transmitted at once. See Figure 2-3. Baseband Baseband is a method of transmitting data in the form of a digital signal, using the entire bandwidth of a cable. Remember that the bandwidth of network media is its total capacity to transmit data, and a digital signal uses the entire bandwidth. Th e network media may be able to support more than one frequency, but in application, it is typically used to carry only one chosen frequency. For example, a copper-core cable may be used to transmit several analog signals, or frequencies, at once, but when used as part of an Ethernet network, will transmit digital signals at only one frequency. Th is frequency will consume the entire bandwidth of the cable. You cannot send two digital signals on the same wire because they have match- ing frequencies and voltage levels. Figure 2-4 illustrates the eff ects of transmitting more than one digital signal on a wire. Each digital signal consists of a pattern of high and low voltage levels, which represent data such as letters and numbers. When both signals are placed on one wire, the two signals combine to form a new digital pattern. Th e new digital pattern of the combined signals cannot be separated into two indi- vidual signals thus, all data is distorted and cannot be read at its destination. 3.3 NET